Related like songs started and/or developed during rehearsals for the Mod Wedding.
Fits in the timeline and subject and could explain the difference in mood and sound.
These demo songs were always a mystery to me, as they never seemed fit into the VU chronology of songs.
But it's just my wild guess, as I've never heard/read anything in that direction.

Those demo's recorded 1966.Nov/Dec in 424 Broome St., source of audio is Sterling's demo disc (acetate?)

I'm not trying to shoot down your theory, but I can't help but wonder what would be the reason, as well as the mechanism, for them having the reel transferred to disc? That would've been costly to have done, so there would've had to have been a concerted reason for it. It seems more likely to me that sessions recorded by themselves would've remained on tape, and those done in a proper studio cut to disc.

In fact, unless the band had access to two tape machines at the same time and place, I think it's entirely possible that multiple copies of their homemade demos were from multiple takes of the material, as opposed to a single, preferred take copied multiple times.

Well whatever the reason and mechanism, 6 of the 7 tracks were transferred to disc at some point, as evidenced by various sources and the photo of Sterl's acetate on p.131 of Unterberger's book.

Unterberger gives a pretty detailed description of the tracks on p.130, and concludes that they could well have been recorded at different times and different places. I'm not entirely convinced - they don't sound as different to my ears as to Unterberger's - but it's certainly possible. If they were it could certainly explain the absence of 'There Is No Reason' from the acetate, and the confusion/contradiction over recording dates and venues.

Lou was always writing songs of a more tender sort. And it seems he had long been intent on recording his songs for posterity or copyright etc. even if they weren't going to be VU songs.

Since I read about Lou recording, or wanting to record a folk album, I have put together a playlist similar to the one mentioned but also featuring the I Found A Reason demo and Countess From Hong Kong which both include harmonica at least and fit well enough with the VU demos. Plays well as an album.

It seems to me that the versions of the Broom St. demos on the PSAS box could be from tape. The other takes that only exist on boot are much noisier and sound like they are from a tape of an acetate.

In Nov '66 we have setlists that show they were not doing any of this material, so the mod-wedding connection seems a little bit speculative. As it is, none of the songs showed up on set-lists aside from "Here She Comes Now' (actually crossed out) in May '67.

With regards why Sterling had a Transco acetate of the songs copied from the tape. It is in keeping with the fact that he had acetates of other songs copied from tape made at later dates. For example, Move Right In.

There is No Reason does seem like the odd one out, just as song.

I don't think these recordings are copyright recordings, as they would just as likely to have been Lou solo on guitar, and also they would have been kept a in sealed stamped posted package.

Who supplied the tape to UMG for the PSAS box? Lou or Cale?

Is there a useful line of enquiry in on what they were recorded? We know that early VU material was taped by Conrad on his deck. We also know that at some point Cale 'acquired' a recorder. Does anyone have dates that relate to Conrad involvement and the date Cale got his own tape recorder? We know that Cale was using a (the acquired?) Wolensack in May 1967 and even has a recording of him and Morrison from that date. (New York In the 60s liner notes).

Broom St. demos
In Nov '66 we have setlists that show they were not doing any of this material, so the mod-wedding connection seems a little bit speculative.

As I commented first, the by me suggested relation between Broom ST. demos (especialy "Here She Comes Now") and the mod-wedding is purely my speculation [never heard, read anything making that connection].
But just today I read the Rolling Stone article from 2018.Jan.30 about WLWH 50years in which is stated:

"5."Here She Comes Now" was originally written to be sung by Nico.
A sequel to Lou Reed’s mysterious character study "Femme Fatale," "Here She Comes Now" was originally intended as a vehicle for Nico... She reportedly sang "Here She Comes Now" at a few live performances, as well; and while there's no recorded version of the song with her on vocals, it’s easy to imagine her Teutonic tones icily caressing lines like "She looks so good/But she’s made out of wood.""

I don't know where above info from RS is sourced from, but actually Nico missing in those Broom St. demos, I considered not supportive of my speculation. As in articles prior to the mod-wedding she's mentioned to be the main singer during the ceremony. Therefore the song written with Nico in mind to sing it, I consider supportive!

Broom St. demos
In Nov '66 we have setlists that show they were not doing any of this material, so the mod-wedding connection seems a little bit speculative.

As I commented first, the by me suggested relation between Broom ST. demos (especialy "Here She Comes Now") and the mod-wedding is purely my speculation [never heard, read anything making that connection].
But just today I read the Rolling Stone article from 2018.Jan.30 about WLWH 50years in which is stated:

"5."Here She Comes Now" was originally written to be sung by Nico.
A sequel to Lou Reed’s mysterious character study "Femme Fatale," "Here She Comes Now" was originally intended as a vehicle for Nico... She reportedly sang "Here She Comes Now" at a few live performances, as well; and while there's no recorded version of the song with her on vocals, it’s easy to imagine her Teutonic tones icily caressing lines like "She looks so good/But she’s made out of wood.""

I don't know where above info from RS is sourced from, but actually Nico missing in those Broom St. demos, I considered not supportive of my speculation. As in articles prior to the mod-wedding she's mentioned to be the main singer during the ceremony. Therefore the song written with Nico in mind to sing it, I consider supportive!

No, it was There She Goes Again that was originally written for Nico to sing, not Here She Comes Now. (Check your RS source again.) And again, it is There She Goes Again that Nico sang live – as captured on the Warhol Rehearsal tapes.

There She Goes Again may have been sung by Nico live, though I’m pretty sure she never tried singing that song again after the initial rehearsal, but it certainly wasn’t written FOR her. It is a 1965 song that predates the meeting of the VU Warhol and Nico.
Here She Comes Now on the other hand seems like it could very well have been written for her. I can imagine her laying there stone-faced (or wood-faced) while Lou fucked her hoping she’d come.

There She Goes Again may have been sung by Nico live, though I’m pretty sure she never tried singing that song again after the initial rehearsal, but it certainly wasn’t written FOR her. It is a 1965 song that predates the meeting of the VU Warhol and Nico.
Here She Comes Now on the other hand seems like it could very well have been written for her. I can imagine her laying there stone-faced (or wood-faced) while Lou fucked her hoping she’d come.

There She Goes Again, may not have been specifically written for her, but out of interest, how do you know it predates her being assigned to the band?